KINETICS OF PHOSPHATE RELEASE FROM A DESERT SOIL

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Abstract
The kinetics of indigenous phosphorus release from the surface and subsoil of Thiokol silt loam, a typic calciorthid, was studied at 11°, 25°, and 40°C. The anion-resin technique was used to obtain the P-release data. The P-release data from the two samples over a period of 5 days could be described by three simultaneous first-order-rate expressions. Three reactions are proposed which could account for the kinetic data. The calculated specific rate constants for any given reaction were similar in both the surface and subsurface soil, suggesting the same reactions were occurring. However, there was a marked difference noted in the total amount of phosphorus released by the soil from the two depths. The effect of temperature on the phosphorus release kinetics was small resulting in activation energies with values between 2 and 3 kcal/m. Thus, the release of phosphorus from this desert soil is not a major energy-consuming process. The parabolic diffusion expression defined P release from the surface and subsoil for only the initial 16 min of reaction. The kinetics of indigenous phosphorus release from the surface and subsoil of Thiokol silt loam, a typic calciorthid, was studied at 11°, 25°, and 40°C. The anion-resin technique was used to obtain the P-release data. The P-release data from the two samples over a period of 5 days could be described by three simultaneous first-order-rate expressions. Three reactions are proposed which could account for the kinetic data. The calculated specific rate constants for any given reaction were similar in both the surface and subsurface soil, suggesting the same reactions were occurring. However, there was a marked difference noted in the total amount of phosphorus released by the soil from the two depths. The effect of temperature on the phosphorus release kinetics was small resulting in activation energies with values between 2 and 3 kcal/m. Thus, the release of phosphorus from this desert soil is not a major energy-consuming process. The parabolic diffusion expression defined P release from the surface and subsoil for only the initial 16 min of reaction. © Williams & Wilkins 1976. All Rights Reserved.

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